1. Field of the Invention
The present invention relates to methods for evaluating and predicting clinical outcomes in patients by measuring levels of protein expression as well as therapies using sIP-10 and its fragments. The present invention also relates to methods for the treatment of infections using CD26 (DPIV) inhibitors. The present invention also relates to methods of monitoring levels of CXCR3 cells in blood, a level of IP-10 and a CD26 activity for assessing patients as to clearing chronic infections and responding to IFN therapy and the necessity of administering CD26 inhibitors.
2. Description of the Background
Hepatitis C virus (HCV) is a significant health problem in that chronic hepatitis occurs in over 50% of infected individuals and may lead to the development of life threatening cirrhosis, hepatic cancer, as well as other sequellae. Chronic hepatitis is often treated with interferon α and/or β and other type I and III interferons that can also be administered in combination with ribavirin with varying levels of success depending on genotypes of the virus.
There are nearly 170 million HCV infected individuals worldwide (1). Many studies have explored the mechanisms by which the immune system is capable of mediating viral clearance (2). Although an HCV-specific humoral response is commonly seen, HCV-specific antibodies are not thought capable of conferring protection (3). Instead, protection in chimpanzees has been shown to correspond with HCV-reactive CD8+ T cell responses. Similarly in humans, a tetramer analysis of successful resolvers indicates the presence of a high frequency of functional HCV-specific CD8+ T cells (4). In addition, there is genetic data to support a role for NK cells based on the higher likelihood of KIR2DL3 and HLA-C1 individuals to clear infection (5). One thing is clear—cure is possible—20-40% of patients spontaneously resolve infection and 40-80% of chronically infected patients (numbers vary depending on viral genotype) that receive peg-IFN-α2/RBV therapy clear the virus and are sustained virologic responders (SVR) (6). Still for many, the virus manages to circumvent natural immunity and our therapeutic strategies, thus resulting in significant morbidity and mortality including liver cirrhosis or hepatocellular carcinoma.
To better define the distinct clinical outcomes of HCV infection many investigators have performed candidate molecule screens or transcriptional profiling in order to identify correlates of viral clearance. One molecule that has gained significant attention is CXCL10 (also known as interferon-gamma induced protein-10 or IP-10), an interferon- and TNFα-inducible chemokine that can be highly expressed by endothelial cells, keratinocytes, fibroblast, mesangial cells, astrocytes, monocytes, neutrophils and hepatocytes (7). In addition to HCV disease, it has been shown to be expressed in many Th1-type inflammatory diseases, often correlating with the target organ infiltration by T cells (8, 9). CXCL10 is a part of a family of α-chemokines that bind CXCR3, which also includes CXCL9 (also known as monokine induced by IFNγ or MIG) and CXCL11 (also known as IFN-inducible T cell α chemoattractant or I-TAC). While all three ligands are induced by IFN and bind the same receptor, there now exists substantial data to support their unique roles in disease pathogenesis. This is clearly evident in chronic HCV, wherein elevated levels of all three have been demonstrated, but only CXCL10 is predictive of a response to the therapy (10).
Regarding published studies of chronic HCV patients, at least five independent cohorts have demonstrated that baseline levels of CXCL10 are predictive of the failure to respond to HCV treatment (10-13). Specifically, this has been demonstrated in patients with genotype 1 and 4 HCV and in the largest study a negative predictive value of 79% was reported for genotype 1 patients (12). In addition, elevated levels of CXCL10 have been reported in patients co-infected by HCV/HIV (14, 15); and with HCV-associated cryoglobulinemia (16). In several of these reports, CXCL10 levels correlate with necroinflammatory activity, fibrosis stage and/or HCV viral load. However, none of the reports have resolved the paradox of why a pro-inflammatory chemokine, responsible for recruiting activated lymphocytes to the liver, is a negative prognostic marker for response to therapy.
The inventors hypothesized that CXCL10 in chronic HCV is catabolized and exists in an antagonist form, thus offering a rationale for its negative impact on treatment responsiveness. Such a mechanism of regulating a chemokine activity has been proposed for several chemokines. Pertinent in vivo examples include the degradation of monocyte chemoattractant protein-3 (MCP-3) by matrix metalloproteinase-2 (MMP-2), reported to be relevant to the pathogenesis of spondyloarthritis (17); and the cleavage of stromal cell derived factor-1 (SDF-1 or CXCL12) in HIV-associated neurodegeneration, also mediated by MMP-2 (18). Herein, the inventors provide direct evidence that the NH2-terminal residues of plasma CXCL10 have been cleaved in HCV patients. Moreover, the inventors have found a correlation between the CXCL10 levels and the precursor frequency of CXCR3+ cells in circulation, indicating in vivo that the chemokine gradient is non-functional. The inventors have investigated matrix metalloprotease (MMP) and dipeptidylpeptidase (DPP) family members as mediators of the truncation and evaluated a role of the enzyme dipeptidylpeptidase IV (DPP4 or CD26). Following from the observations, the inventors have found an important link between the metabolic complications and the chronic inflammation seen in HCV patients. The inventors have determined that DPP4 is a novel therapeutic target, inhibition of which results in the restoration of the CXCL10 gradient and allows for increased responsiveness to peg-IFN-α2/RBV therapy.
Even with interferon therapies, there are substantial side effects, and the costs of therapy are very high. Accordingly, there is a need to develop a way to assess when successful results can be expected in an individual patient with a particular IFN therapy.
Thus, an object of the invention is to provide a way in which to predict whether such therapies would be useful for treating certain patients and also a treatment of infections using CD26 (DPIV) inhibitors.